The Individualised Niche in Motion; quantifying individualised niches with movement data

Elina Takola 

Individuals of the same species often differ consistently in their use of resources, their responses to environmental gradients, and their movement decisions. Between-individual variation across niche axes has been shown to have important ecological consequences. Yet practical frameworks that translate modern tracking data into operational, comparable measures of niche individual specialisation remain limited. Rather, the individualised niche concept has inherited the plasticity of the ecological niche concept and its quantification has been considered an unfeasible goal. Here I present a workflow that estimates realised and potential individualised niches from movement data using mixed-effects selection functions. The workflow combines resource selection models with random intercepts and slopes with relative selection probabilities and ecological niche indices. Individualised niches are quantified using niche breadth and pairwise niche overlap are derived from hypervolume representations in environmental space and provide interpretable measures of specialisation. In addition, I use repeatability estimates, which capture consistent among individual differences in the use of single environmental axes and allow direct comparisons between realised and potential niche components. The workflow is implemented in exclusively in the programming language R. A case study using publicly available northern lapwing (Vanellus vanellus) tracking data illustrates how the workflow can be applied across multiple environmental variables (earthworm abundance, human population density, cropping intensity, application rates of glyphosates and propiconazole, air temperature, precipitation, wind speed, soil water index, human footprint, organic carbon, soil bulk density, soil nitrogen, crop type and NDVI) to characterise individualised niches.